The antonyms for the word "most unhurtful" are numerous, including harmful, damaging, hurtful, dangerous, injurious, destructive, detrimental, and pernicious. These words indicate actions or situations that are detrimental to one's well-being, causing harm or injury in various ways. For instance, people can cause harm by spreading rumors or gossiping, leaving a harmful impact on the victim. Similarly, chemical toxins, unhealthy diets, and environmental pollutants can also be damaging, causing long-term health issues. Therefore, it is crucial to be cautious and mindful of these antonyms to avoid negative consequences and maintain physical and mental well-being.